Efficient production of succinic acid using Mannheimia succiniciproducens and the study for the industrialization of bio-based succinic acid

Abstract

In response to the global issues, including global warming and climate change, efforts to reduce greenhouse gas emission, such as regulation of total carbon emission, are taking place. In addition, with recent advances in systems metabolic engineering technology, various genetically modified microorganisms capable of efficiently produce target chemicals using the non-food biomass were developed. Succinic acid (SA) is a four-carbon dicarboxylic acid of industrial importance that is widely studied for the bio-based production. Mannheimia succiniciproducens is a capnophilic rumen bacterium capable of efficiently producing SA. Numerous studies on development of this microorganism to produce high amount of SA with almost no byproducts have been reported. In this dissertation, for successful industrialization of bio-based SA production process, systems metabolic engineering approach was applied to engineer M. succiniciproducens to efficiently produce SA. For this, metabolic pathway is optimized for enhanced SA production and auxotrophs that exists in M. succiniciproducens are removed to reduce components included in the chemically defined medium. Furthermore, simpler and cheaper downstream processes are developed to decrease the SA production cost. To evaluate the feasibility of fermentative SA production in large scale fermenter, pilot-scale fermentations were conducted and various fermentation techniques were applied. To verify the industrial application of bio-based SA, an efficient process for the separation and purification of diamines from fermentation broth was developed. With the purified bio-based diamines and SA, synthesis and characterization of bionylon-4,4 and -5,4, two rarely studied nylons, were produced. The strategy for the synthesis of fully bio-based nylons and application reported here can serve as a guideline for synthesizing other fully bio-based polymers from renewable resources. This study demonstrated the feasibility of efficient bio-based SA production using metabolic engineering of M. succiniciproducens and the possibility of successful industrialization by scale-up the bioprocess and the validation of actual applications of bio-based SA.